Electric forklifts, as one of the important pieces of equipment in the modern warehousing and logistics industry, have gradually replaced traditional internal combustion forklifts due to their high efficiency and environmental friendliness. The battery, a core component of the electric forklift, directly affects the forklift's working efficiency, service life, and safety. Therefore, proper battery maintenance and charging management are crucial for extending the service life of electric forklifts. This article, from the perspective of a heavy-duty vehicle maintenance engineer, will detail the precautions for battery and charging maintenance after daily operation of electric forklifts.
1.1 Power Disconnection and Isolation
After operation, immediately turn off the main power switch, remove the key, and ensure the vehicle is in a "power-off locked" state to prevent short circuits caused by accidental operation.
1.2 Check Battery Charge Level and Voltage
After each use of the electric forklift, the first step is to check the battery's charge level and voltage. This not only helps determine the current state of the battery but also allows for timely detection of potential battery problems. If the battery charge is too low, it should be charged promptly to avoid over-discharge. Over-discharge will affect the battery's charging efficiency and lifespan.
1.3 Clean Battery Terminals
Regular cleaning of the battery terminals is an important part of battery maintenance. Check whether there are white or green crystals (lead sulfate corrosion) on the positive and negative terminals. If found, record it immediately and proceed with the cleaning process. Dirt and corrosion on the battery terminals can lead to poor contact, which in turn affects the battery's charging and discharging performance. When cleaning, use a clean, soft cloth and avoid using corrosive cleaning agents to prevent damage to the terminals. If necessary, a battery terminal protector can be used to prevent terminal oxidation.
1.4 Check Battery Appearance
Regularly check the battery's appearance, paying attention to any signs of leakage, swelling, or damage. Check the battery casing for bulging, cracks, and traces of electrolyte leakage; pay particular attention to whether the drainage holes at the bottom of the battery box are blocked to prevent water accumulation and corrosion of the chassis. If any abnormalities are found in the battery, they must be addressed immediately. The battery may experience thermal runaway due to prolonged use, leading to leakage, bubbling, or even explosion. Therefore, maintaining the battery casing intact and preventing the battery from being subjected to external impact is crucial. 1.5 Temperature Monitoring
The operating temperature of the battery significantly affects its performance. If the battery casing (excluding the terminals) feels continuously hotter than 45°C, further operation should be suspended, and the battery should be allowed to cool down to below 35°C to prevent thermal runaway. Excessively high temperatures accelerate battery aging and shorten battery life. Therefore, after prolonged use, ensure the battery has sufficient cooling time. Avoid parking the electric forklift in high-temperature environments, such as direct sunlight or near heat sources.
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Maintenance Project |
Operating Procedures |
Tools and Materials |
frequency |
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Electrolyte level check |
When measuring with a transparent glass tube, the liquid level should be 15–25 mm above the electrode plate; it is strictly forbidden to be below the upper edge of the electrode plate. |
Distilled water (GB6682), glass tubes, droppers |
After daily charging |
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Hydration procedure |
Only distilled water is allowed to be added; after adding water, let it stand for 2 hours before charging to prevent concentration separation. |
Acid-resistant dropper, acid-resistant gloves, safety goggles |
daily |
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Terminal cleaning |
Lightly abrade the corrosive material with fine sandpaper (120 grit or higher), then apply a special anti-corrosion grease (such as petroleum jelly or lithium-based grease). |
Insulating sandpaper, cotton cloth, anti-corrosion grease |
weekly |
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Connection fastening |
Use a torque wrench to tighten the terminal bolts; the standard torque is 15–20 N·m. Loosening will cause increased contact resistance and lead to localized overheating. |
Digital torque wrench (0–50 N·m) |
weekly |
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Battery box drainage |
Clean the drain holes at the bottom of the battery compartment, ensuring they are free of dust and rust; it is recommended to use compressed air to blow them out. |
Compressed air gun (≤0.3MPa) |
weekly |
When humidity >85%, terminal corrosion accelerates. It is recommended to add 5% graphite powder to the anti-corrosion grease to improve conductivity and moisture resistance.
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Maintenance Project |
Operating Procedures |
Precautions |
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BMS Status Check |
Read the following using an onboard HMI or handheld diagnostic tool: Individual cell voltage difference ≤ 50mV, maximum temperature ≤ 45℃, and SOC fluctuation ≤ ±3%. |
Forced charging is prohibited when the BMS reports "Cell Imbalance" or "Over Temp". |
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Cleaning the charging port |
Wipe the metal contacts of the plug and socket with a non-woven cloth and 99% isopropyl alcohol; do not use water or chlorine-containing cleaners. |
After each shift, especially in dusty environments (such as steel mills and cement plants), |
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Thermal management inspection |
Confirm that the battery pack cooling fan is working properly and that there is no dust buildup at the air intake; clean the heat sink fins monthly with compressed air. |
Summer temperatures in Chongqing often exceed 38°C, so it is necessary to ensure that the temperature of the air-conditioned charging room is controlled at 25±3°C. |
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Deep discharge is prohibited. |
The state of charge (SOC) must not be lower than 10%; the device must be charged immediately when the red warning light on the instrument panel illuminates to avoid irreversible capacity degradation caused by over-discharge of individual cells. |
Lithium batteries do not have a "memory effect," but over-discharge can trigger the BMS lock-up protection. |
Industrial-grade lithium iron phosphate (LFP) batteries have a cycle life of over 4000 cycles under typical operating conditions, but BMS failure will lead to a lifespan reduction of more than 50%.
4.1 Selecting the Appropriate Charging Equipment
The charging equipment for electric forklift batteries should meet the manufacturer's requirements. Using inappropriate charging equipment may not only affect charging efficiency but also lead to battery damage or safety hazards. Therefore, the charging equipment must match the battery's voltage and capacity specifications to ensure stability and safety during the charging process.
4.2 Avoiding Overcharging
Overcharging causes excessive heat generation inside the battery, accelerating battery aging and reducing its lifespan. Modern batteries usually have an automatic power-off function, but the battery status should still be checked regularly during charging to avoid leaving the battery connected to the charger for extended periods.
4.3 Charging Time Control
Charging time should be strictly controlled according to the battery specifications and user manual. Generally, battery charging should be kept between 20% and 80%. Overcharging or over-discharging will have adverse effects on the battery. Ensuring the battery is charged within the optimal charge range can effectively extend its lifespan.
4.4 Regular Deep Charging
Although electric forklifts generally use lithium-ion or lead-acid batteries, regular deep charging still helps to eliminate the battery's memory effect and maintain its high performance. Generally, performing a deep charge every few months can help the battery maintain its optimal performance. 4.5 Charging Environment Management
Charging should be carried out in a well-ventilated environment to prevent battery overheating or the generation of harmful gases during the charging process. In cold weather conditions, the temperature of the charging room should be maintained within a suitable range to prevent low battery temperature from affecting charging efficiency.
Smoking and open flames are strictly prohibited in the charging area. Carbon dioxide fire extinguishers should be provided (water-based or dry powder fire extinguishers are prohibited).
4.6 Charger Operation Specifications
Lead-acid batteries: A smart charger with a matching voltage (e.g., 48V/80Ah) must be used, following a three-stage process: "standard charging → float charging for 1 hour → automatic equalization charging".
Lithium-ion batteries: Only original manufacturer BMS-compatible chargers are allowed; the use of general-purpose "fast charging" devices is prohibited.
Equalization charging: For lead-acid batteries, this should be performed once every 300 cycles; for lithium batteries, it is automatically triggered by the BMS and should not be manually interfered with by maintenance personnel.
Post-charging operation: After the charging completion indicator light turns on, maintain the connection for 1 hour to ensure float charging equalization. Before unplugging the charging plug, turn off the charger power first, then disconnect the battery terminals to prevent arc damage to the connector.
5.1 Battery Replacement Timing
With prolonged use, the capacity and performance of the battery will gradually decline. When the battery reaches a certain limit of its service life, the number of charging cycles will significantly decrease, or the battery power will be insufficient to meet operational needs. At this point, battery replacement should be considered. Timely replacement of aging batteries ensures the normal operation of the forklift.
5.2 Battery Recycling and Environmentally Friendly Disposal
Used batteries should not be discarded indiscriminately. Lead-acid batteries and lithium batteries are electronic waste containing hazardous substances and should be processed through professional recycling channels. According to relevant regulations, the recycling and environmentally friendly disposal of battery waste is very important and helps reduce environmental pollution. 6. Prohibited Actions
❌ Strictly prohibited to move the forklift or start the equipment during charging.
❌ Strictly prohibited to use tap water, mineral water, or industrial water to replenish lead-acid batteries.
❌ Strictly prohibited to place metal tools (wrenches, screwdrivers) on top of the battery.
❌ Strictly prohibited to charge unattended overnight in poorly ventilated conditions.
❌ Strictly prohibited to mix battery packs of different brands, capacities, or types.
❌ Strictly prohibited to disassemble the lithium battery BMS module or replace battery cells without authorization.
As a high-efficiency equipment, the maintenance and charging management of electric forklifts' batteries are crucial for ensuring their long-term stable operation. Through daily inspections, correct charging, and reasonable battery replacement, the battery life can be effectively extended, work efficiency can be improved, and maintenance costs can be reduced. As a maintenance engineer, paying attention to battery maintenance and charging management is not only responsible for the equipment itself but also a guarantee for the efficiency of enterprise operations.
